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              <h1>HotSpot GC的分类 - 交互式测验</h1>
              <p>检验你对文档内容的理解程度</p>
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  {
    "question": "根据文档，串行垃圾收集器（Serial GC）最适合的应用场景是什么？",
    "options": [
      "需要极低延迟的大型企业级应用",
      "单核处理器或内存资源非常有限的环境",
      "追求最大化吞吐量的多核服务器",
      "需要并发执行垃圾回收以避免停顿的场景"
    ],
    "correctAnswerIndex": 1,
    "explanation": "串行垃圾收集器使用单个线程执行所有垃圾回收工作，这使得它在多核CPU上无法充分利用硬件资源。然而，其简单高效的设计和较低的额外开销，使其非常适合CPU核心数少（如单核）或内存较小的客户端机器或嵌入式设备。",
    "source": "文档中「1. 串行垃圾收集器（Serial GC）」部分",
    "hint": "思考一下“串行”这个词在计算中通常意味着什么，以及它对多核处理器的影响。"
  },
  {
    "question": "并行垃圾收集器（Parallel GC）的核心设计目标是什么？",
    "options": [
      "尽可能减少单次GC的停顿时间，实现最低延迟",
      "在应用程序运行时并发执行GC，避免应用暂停",
      "提高应用程序的总体吞吐量，即CPU用于运行用户代码的时间最大化",
      "解决老年代的内存碎片问题"
    ],
    "correctAnswerIndex": 2,
    "explanation": "并行垃圾收集器（也常被称为“吞吐量优先收集器”）的设计目标是最大化应用程序的吞吐量。它通过并行使用多个GC线程来缩短垃圾回收的总时间，尽管这会导致应用在GC期间完全暂停（Stop-The-World），但其目标是降低GC时间占总运行时间的比例，从而让应用代码获得更多的执行机会。",
    "source": "文档中「2. 并行垃圾收集器（Parallel GC）」部分",
    "hint": "文档中明确指出了这款收集器是“吞吐量优先”的。"
  },
  {
    "question": "尽管并发标记-清除（CMS）收集器旨在降低停顿时间，但它存在一个显著的缺点。根据文档，这个缺点是什么？",
    "options": [
      "GC过程是单线程的，导致效率低下",
      "会造成非常长的应用程序停顿，影响响应性",
      "可能导致老年代产生内存碎片",
      "它比其他所有收集器都需要更多的内存资源"
    ],
    "correctAnswerIndex": 2,
    "explanation": "CMS收集器采用“标记-清除”算法。在清除阶段，它仅回收被标记为垃圾的对象所占用的空间，但不会移动存活的对象来整理内存。长此以往，这会导致堆内存中出现大量不连续的空闲空间，即内存碎片。当需要为大对象分配空间时，可能会因为没有足够大的连续空间而提前触发一次Full GC。",
    "source": "文档中「3. 并发标记-清除垃圾收集器（CMS）」的「缺点」部分",
    "hint": "请关注CMS的“缺点”小节，其中提到了一个与内存空间布局相关的问题。"
  },
  {
    "question": "与CMS相比，G1垃圾收集器通过哪种核心机制来解决内存碎片问题？",
    "options": [
      "它将堆内存划分为多个区域（Region），并通过复制存活对象来完成回收和整理",
      "它在所有阶段都暂停应用程序以进行一次彻底的内存整理",
      "它采用了更先进的并发标记算法，从而避免了碎片的产生",
      "它完全禁止大对象的分配"
    ],
    "correctAnswerIndex": 0,
    "explanation": "G1收集器从根本上改变了内存的组织方式。它将整个Java堆划分为多个大小相等的独立区域（Region）。在进行垃圾回收时，G1会将一个或多个Region中的存活对象复制到其他空的Region中。这个复制的过程本身就完成了内存的整理和压缩，从而自然地解决了内存碎片问题。",
    "source": "文档中「4. Garbage-First（G1）垃圾收集器」部分",
    "hint": "G1的特点中提到了“分区”和“高效整理”，思考一下它是如何实现整理的。"
  },
  {
    "question": "ZGC（Z Garbage Collector）最突出的设计目标和特点是什么？",
    "options": [
      "以牺牲延迟为代价，实现最高的吞吐量",
      "在单核CPU上实现最高的收集效率",
      "提供几乎零停顿的极低延迟垃圾回收",
      "尽可能减少JVM的内存占用，适用于小型设备"
    ],
    "correctAnswerIndex": 2,
    "explanation": "ZGC的设计目标非常明确，就是为了在处理大规模内存（TB级别）的同时，提供极低的、可预测的停顿时间（通常在几毫秒以内），几乎达到“零停顿”的效果。它通过先进的并发技术，使得包括标记、整理在内的绝大多数GC工作都能与应用线程并发执行，从而实现了这一目标。",
    "source": "文档中「5. Z Garbage Collector（ZGC）」部分",
    "hint": "文档描述ZGC的目标是提供「几乎零停顿的垃圾回收」，这对应了哪个性能指标？"
  },
  {
    "question": "在垃圾收集器的语境中，“并发”（Concurrent）一词的确切含义是什么？",
    "options": [
      "垃圾收集器使用多个线程执行工作，但会完全暂停应用程序",
      "垃圾收集器的部分或全部工作可以在应用程序线程运行的同时进行",
      "垃圾收集器只在CPU空闲时运行",
      "应用程序必须显式地调用GC来触发并发回收"
    ],
    "correctAnswerIndex": 1,
    "explanation": "“并发”指的是垃圾收集线程与应用程序线程可以同时运行。像CMS、G1、ZGC和Shenandoah这样的并发收集器，其设计目标就是尽量减少因GC而需要暂停应用程序（即“Stop-The-World”）的时间。它们通过复杂的算法，使得标记、清除或整理等耗时操作可以与用户代码并行执行。",
    "source": "文档中「3. CMS」、「4. G1」、「5. ZGC」、「6. Shenandoah」等部分",
    "hint": "观察CMS的描述：“在应用程序运行的同时进行垃圾收集”，这句话揭示了“并发”的核心思想。"
  },
  {
    "question": "如果一个应用程序的首要性能指标是“高吞吐量”，即使偶尔出现较长的GC停顿也可以接受，那么根据文档，哪款垃圾收集器是理论上的最佳选择？",
    "options": [
      "串行GC (Serial GC)",
      "并发标记-清除GC (CMS)",
      "并行GC (Parallel GC)",
      "Shenandoah GC"
    ],
    "correctAnswerIndex": 2,
    "explanation": "并行GC（Parallel GC）的设计目标就是最大化吞吐量。它利用多核CPU的优势，并行地进行垃圾回收，虽然会“Stop-The-World”，但其GC总时间占应用运行总时间的比例较低，从而让应用程序代码获得更长的运行时间，提高了整体吞吐量。而CMS、Shenandoah等则更侧重于降低停顿时间。",
    "source": "文档中「2. 并行垃圾收集器（Parallel GC）」部分",
    "hint": "文档中明确指出有一款收集器的设计目标是「提高应用程序的吞吐量」。"
  }
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                '<tr><td>正确</td><td>' + correctCount + '</td></tr>' +
                '<tr><td>错误</td><td>' + wrongCount + '</td></tr>' +
                '<tr><td>未答</td><td>' + skippedCount + '</td></tr>' +
                '</table>' +
                '</div>' +
                '</div>' +
                '<div class="report-actions">' +
                '<button id="review-btn">回顾测验</button>' +
                '<button class="primary" onclick="location.reload()">再试一次</button>' +
                '</div>' +
                '</div>';

            let reportEl = document.querySelector('.final-score-container');
            if (reportEl) {
                reportEl.remove();
            }
            quizContentEl.insertAdjacentHTML('beforeend', finalScoreHtml);
            document.getElementById('review-btn').addEventListener('click', reviewQuiz);
        }

        function reviewQuiz() {
            const reportEl = document.querySelector('.final-score-container');
            if (reportEl) {
                reportEl.remove();
            }

            document.querySelector('.quiz-body').style.display = 'block';
            document.getElementById('quiz-footer').style.display = 'flex';
            
            currentQuestionIndex = 0;
            loadQuestion();
            updateNavigationButtons(); // Ensure nav buttons are correctly displayed
        }

        // Event Delegation for options
        optionsListEl.addEventListener('click', (event) => {
            if (event.target && event.target.matches('li.option-item')) {
                // Check if the question has already been answered
                if (userAnswers[currentQuestionIndex] === null) {
                    const selectedIndex = parseInt(event.target.dataset.index, 10);
                    selectOption(selectedIndex);
                }
            }
        });

        prevBtn.addEventListener('click', goToPreviousQuestion);
        nextBtn.addEventListener('click', goToNextQuestion);
        hintBtn.addEventListener('click', showHint);
        
        // 初始加载
        loadQuestion();
      </script>
    </body>
    </html>
  